In order to determine quality of a pattern formed on a surface of a semiconductor wafer, there are proposed various methods in which a sectional shape is measured by observation with Scanning Electron Microscope (SEM). In the observation of the sectional shape with SEM, the pattern on an inspected substrate is scanned in a sectional direction of the pattern with an electron beam, reflection electrons or secondary electrons from the pattern are detected and analyzed to obtain the sectional shape of the scanned portion. The operation is performed for several points on the pattern to determine the quality of the pattern shape as a whole.
As another method for determining the quality of the pattern an in-line measurement technique of measuring CD or an overlay with a scatterometer can also be cited.
In a spectral scatterometer, a scattered-light characteristic is measured at a fixed angle as a function of a wavelength, and usually a broadband light source such as a xenon lamp, a deuterium lamp, and a halogen-system light source such as a xenon-arc lamp is used. Either perpendicular incidence or oblique incidence may be used as the fixed angle.
In an angle-resolved scatterometer, the scattered-light characteristic is measured at a fixed wavelength as a function of an incident angle, and usually a laser beam is used as a single-wavelength light source.
Patent Document 1: Japanese Patent Publication Laid-Open No. 2005-188944
In the measurement method with SEM, because operations of irradiating and scanning the pattern with electron beam are repeatedly performed many times, a huge amount of time is required to obtain the pattern shape. All the pattern shapes on the wafer are hardly obtained due to high observation magnification, and some points are sampled to determine the quality of the whole wafer. As a result, a defect is overlooked if the defect is located in a portion except for the sample patterns. When a resist pattern is irradiated with electron beam, the resist absorbs the electron beam by an acceleration voltage, and the resist is charged up to generate deterioration of the pattern. In some cases, a discharge is generated to bring down the pattern, and inconvenience is generated in subsequent processes. Therefore, an optimum observation condition is obtained while the acceleration voltage or the observation magnification is changed in various ways. Thus, additional time is required for measurement.
One of problems of the angle-resolved scatterometer technique is that only one wavelength is detected in each time. Accordingly, when the spectrum has plural wavelengths, it is necessary to perform time-division multiplex of the wavelength, which increases the total time necessary to detect and process the spectrum. In the spectral scatterometer, it is necessary that a small grating be illuminated by light with small spread of incident angle, which wastes a large amount of light from the diffuse light source. Accordingly, a light level is decreased on a detector to lengthen the obtaining time, which adversely affects throughput. When a short obtaining time is selected, sometimes measurement result becomes unstable.
In view of the foregoing, a problem of the present invention is to provide surface inspecting apparatus and a surface inspecting method which can make a distinction between the acceptable and defective pattern shapes on the inspected substrate in a short time irrespective of a resist pattern and a post-etching pattern.